Method and system for encoding color images to black-and-white bitmaps and decoding color images

Abstract

A method and system for encoding a color image into a monochrome halftoned image for printing, includes the use of a decoding mechanism to recover color information from the monochrome halftone image. A luminance channel associated with the color image can be utilized as the grayscale input to a half-toning process, while chrominance channels are utilized to determine displacements of the halftone dots. The color information can then be restored utilizing a template to measure the displacements of the halftone dots and hence the color information. Thus, the color information can be preserved without visual impact.

1. A method for encoding color images to black and white bitmaps and decoding back to color, comprising:
 encoding a color image by producing a monochrome halftone image based on said color image; 
 rendering said monochrome halftone image as a hardcopy; and 
 reconstructing and aligning said monochrome halftone image in order to produce an aligned halftone image for use in reconstructing and rendering said color image. 
 
   
   
     2. The method of  claim 1  wherein encoding said color image comprises:
 converting said color image to an intermediate color space; 
 extracting a luminance from said intermediate color space and identifying screen-shifted non-luminance components thereof; and 
 half-toning said luminance and screen-shifted non-luminance components. 
 
   
   
     3. The method of  claim 2  further comprising:
 subjecting said screen-shifted non-luminance components to a dot displacement mapping wherein dot displacements thereof are screen shifted. 
 
   
   
     4. The method of  claim 1  further comprising decoding said color image by:
 estimating said aligned halftone image utilizing grayscale data; 
 extracting said luminance from said aligned halftone image based on said grayscale data; 
 reconstructing non-luminance components from said aligned halftone image; and 
 thereafter reconstructing said color image in response to reconstructing said non-luminance components, extracting said luminance, and estimated said aligned halftone image. 
 
   
   
     5. The method of  claim 4  wherein reconstructing said non-luminance components comprises:
 generating a plurality of dot templates; 
 analyzing said plurality of dot templates for dot template matching; and 
 performing an inverse dot displacement mapping with respect to said plurality of dot templates in order to assist in reconstructing said non-luminance components. 
 
   
   
     6. The method of  claim 5  further comprising optimizing said dot displacement mapping in order to preserve neutral colors thereof. 
   
   
     7. The method of  claim 1  further comprising scanning and binarizing said hardcopy in response to rendering said monochrome halftone image as a hardcopy. 
   
   
     8. A system for encoding color images to black and white bitmaps and decoding back to color, comprising:
 a data-processing apparatus; 
 at least one module executed by said data-processing apparatus, said at least one module and said data-processing apparatus being operable in combination with one another to:
 encoding a color image by producing a monochrome halftone image based on said color image; 
 rendering said monochrome halftone image as a hardcopy; 
 storing said monochrome halftone image for later use; 
 transferring said monochrome halftone image through at least one narrow-bandwidth channel; and 
 reconstructing and aligning said monochrome halftone image in order to produce an aligned halftone image for use in reconstructing and rendering said color image. 
 
 
   
   
     9. The system of  claim 8  wherein said data-processing apparatus and said at least one module are further operable in combination with one another to encode said color image by:
 converting said color image to an intermediate color space; 
 extracting a luminance from said intermediate color space and identifying screen-shifted non-luminance components thereof; and 
 half-toning said luminance and screen-shifted non-luminance components. 
 
   
   
     10. The system of  claim 9  wherein said data-processing apparatus and said at least one module are further operable in combination with one another to subject said screen-shifted non-luminance components to a dot displacement mapping wherein dot displacements thereof are screen shifted. 
   
   
     11. The system of  claim 8  wherein said data-processing apparatus and said at least one module are further operable in combination with one another to decode said color image by:
 estimating said aligned halftone image utilizing grayscale data; 
 extracting said luminance from said aligned halftone image based on said grayscale data; 
 reconstructing non-luminance components from said aligned halftone image; and 
 thereafter reconstructing said color image in response to reconstructing said non-luminance components, extracting said luminance, and estimated said aligned halftone image. 
 
   
   
     12. The system of  claim 11  wherein said data-processing apparatus and said at least one module are further operable in combination with one another to reconstruct said non-luminance components by:
 generating a plurality of dot templates; 
 analyzing said plurality of dot templates for dot template matching; and 
 performing an inverse dot displacement mapping with respect to said plurality of dot templates in order to assist in reconstructing said non-luminance components. 
 
   
   
     13. The system of  claim 11  wherein said data-processing apparatus and said at least one module are further operable in combination with one another to optimize said dot displacement mapping in order to preserve neutral colors thereof. 
   
   
     14. The system of  claim 8  further wherein said data-processing apparatus and said at least one module are further operable in combination with one another to scan and binarize said hardcopy in response to rendering said monochrome halftone image as a hardcopy. 
   
   
     15. A program product residing in a computer for encoding color images to black and white bitmaps and decoding back to color, comprising:
 instruction media residing in a computer for encoding a color image by producing a monochrome halftone image based on said color image; 
 instruction media residing in a computer for rendering said monochrome halftone image as a hardcopy; and 
 instruction media residing in a computer for reconstructing and aligning said monochrome halftone image in order to produce an aligned halftone image for use in reconstructing and rendering said color image. 
 
   
   
     16. The program product of  claim 15  wherein said instruction media residing in a computer for encoding said color image further comprises:
 instruction media residing in a computer for converting said color image to an intermediate color space; 
 instruction media residing in a computer for extracting a luminance from said intermediate color space and identifying screen-shifted non-luminance components thereof; and 
 instruction media residing in a computer for half-toning said luminance and screen-shifted non-luminance components. 
 
   
   
     17. The program product of  claim 16  further comprising:
 instruction media residing in a computer for subjecting said screen-shifted non-luminance components to a dot displacement mapping wherein dot displacements thereof are screen shifted. 
 
   
   
     18. The program product of  claim 15  further comprising instruction media residing in a computer for decoding said color image, wherein said instruction media further comprises:
 instruction media residing in a computer for estimating said aligned halftone image utilizing grayscale data; 
 instruction media residing in a computer for extracting said luminance from said aligned halftone image based on said grayscale data; 
 instruction media residing in a computer for reconstructing non-luminance components from said aligned halftone image; and 
 instruction media residing in a computer for thereafter reconstructing said color image in response to reconstructing said non-luminance components, extracting said luminance, and estimated said aligned halftone image. 
 
   
   
     19. The program product of  claim 18  wherein said instruction media residing in a computer for reconstructing said non-luminance components further comprises:
 instruction media residing in a computer for generating a plurality of dot templates; 
 instruction media residing in a computer for analyzing said plurality of dot templates for dot template matching; and 
 instruction media residing in a computer for performing an inverse dot displacement mapping with respect to said plurality of dot templates in order to assist in reconstructing said non-luminance components. 
 
   
   
     20. The program product of  claim 15  further comprising instruction media residing in a computer for scanning and binarizing said hardcopy in response to rendering said monochrome halftone image as a hardcopy.